I was planning an upgrade from 26 to 650b on my 2013 enduro as I had the chance to get new seat/chain stays and yoke. I bought a CCDB inline to run 650b and ran it on the bike in 26 mode without any problems at all. The shock is shorter eye to eye marginally so slackened the HA very slightly.
In the end I went for a new 650 enduro as the deal for the parts fell through. I had the option of Monarch debonair or inline on the new frame and stayed with the CCDB. no problems with it at all.
If i remember correctly the E29 and 650 have the same shock size.
Drop me a line if you are interested in an inline as I have a spare brand new one that I could part with.